She says the problem is with the color of the light – blue — coming from those devices. It also is emitted by energy-efficient light bulbs.

“Blue light is a very powerful wavelength of light for the brain” Zee says.

Exposure during the day can actually help you fall asleep at night by stimulating a brain chemical called melatonin. But, exposure in the evening suppresses melatonin.

“It can make you, for example, go to bed later,” Zee says. “So, you’re more likely to get insomnia symptoms, difficulty falling asleep.”

Getting to bed late can lead to a host of other problems, too, including depression, high blood pressure and obesity. Research from Northwestern shows that it can even change what we eat.

Harvard University’s Dr. Steven Lockley says cancer is a real threat among some people whose body clocks are chronically out of whack.

How can you stay healthy?

Zee suggests turning down the brightness level on your device, and try to put your devices away two hours before bedtime.

Jordan cut back on screen time, and she says the results have been eye-opening.

“It was fabulous. I found myself feeling much more relaxed,” she says.

There are also some apps that allow you to change your device’s traditional blue light screen to a healthier red or yellow light. You can also wear amber-tinted sunglasses while using your device at night.